The goal of the proposed research is to understand how communication between cells contributes to developmental processes. Genetic, molecular, and cell biological techniques will be employed to study the cell-cell interactions in the fruit fly Drosophila melanogaster that coordinate the migrations of the follicle cells during their production of the eggshell (or chorion). I will focus my efforts on characterizing a network of genes required to produce the two dorsolateral respiratory appendages, or filaments. Previous work has established a model for the events that initiate production of the dorsal filaments. This proposal examines the next step in that pathway: the transduction of the germ line signal by the dorsal follicle cells, resulting in the proper positioning of those cells at the anterior end of the egg chamber, where they lay down the chorion composing the base of the dorsal appendages. We identified two lethal mutations whose ovarian expression is limited to the dorsal follicle cells in late stage ten egg chambers, l(2)4745 and l(3)0836. Finally, approximately 70 enhancer patterns have been selected that will be useful for characterizing the filament pathway. The major thrust of this proposal focuses on rhino and fs(2)2013. Several specific phenotypic assays will establish where and when these genes act and will provide a basis for characterizing their mode of action. Analysis of mosaics generated by mitotic recombination and pole cell transplantation, in situ hybridization to ovarian tissue sections, and Northern blot analysis will provide spatial and temporal information concerning their expression. Observation of the migrations of the follicle cells in vitro culture will examine the mechanism used by the follicle cells to interpret the spatial coordinate system and thereby position the dorsal filaments correctly. Sequence analysis may provide a clue to these genes functions by homology to known proteins. Cellular localization of the proteins will be established by analysis with antibodies generated to fusion peptides. These genes may interact directly with the torpedo tyrosine kinase receptor to facilitate a cascade of events required for filament formation, or they may act downstream of such events and their expression may be activated in a gradient-specific fashion by the binding of factors to a concentration-sensitive promoter. The proposed experiments combine genetic, molecular and cell biological techniques to ascertain one of the steps by which an initiating signal is transplanted into directed cell movement and coupled to the ordered expression of the chorion genes to yield the dorsal filaments. These studies therefore examine the process by which cells transmit, receive, and interpret positional information and direct the ordered process of development.